This section provides background information related to the present disclosure which is not necessarily prior art.
Power transfer devices of the type used in automotive applications, such as for example, automatic transmissions, torque couplings, power take-off units and transfer cases, are commonly equipped with a power-operated multi-plate clutch assembly. Typically, the multi-plate clutch assembly includes a first clutch member (such as a clutch hub) driven by an input component, a second clutch member (such as a clutch drum) driving an output component, a multi-plate clutch pack disposed therebetween, and a powered clutch actuator for engaging the clutch pack and transmitting drive torque from the clutch hub to the clutch drum. The clutch drum and clutch hub are typically annular components having torque-transmitting spline teeth that are configured to engage and mesh with corresponding clutch teeth formed on the clutch plates of the clutch pack.
To reduce the mass of such clutch members while maintaining the required high-strength and torque transmission characteristics, many modern clutch hubs and drums, hereinafter referred to cumulatively as annular clutch components, are formed from sheet-metal blanks using a combination of various metal-forming and metal-cutting processes. Non-limiting examples of current high volume processes for manufacturing annular clutch components include Grob spline processing and flow form processing.
Due to the design of these formed sheet-metal clutch components, the currently available processes also present several known shortcomings. Specifically, the annular clutch components are initially formed from a steel blank that is drawn into a cup-shaped component having a radial plate segment and an axially-extending hub segment. The cup-shaped component is subsequently formed over a mandrel to produce a spline form in the hub segment via the Grob splining process. The start of the spline form from the flat flange segment to the outer diameter is in the form of a radius with a large radius on the major OD and a smaller radius on the minor OD. Typically, the annular clutch component requires an additional metal-cutting or machining process after forming the splines to form a mounting segment on the plate segment configured to allow subsequent welding or joining of another torque transmitting component. In order to guarantee the flatness of the plate segment of the annular clutch component, a metal-cutting machining process is also typically required. However, machining of the plate segment requires the cutter tool to cut along the entire length of the plate segment and encounter the edge of the spline form on both the major and minor OD surfaces. This “cut” edge profile results in an interrupted cut which, in turn, causes the machined edge material to be pushed down into the spline form as a burr. As such, a subsequent deburring operation is required to remove the burrs in the spline form area. Burrs that are not removed prior to assembly of the clutch assembly can have a detrimental impact on the function and service life of the clutch assembly.
To this end, a need exists to develop a metal forming process capable of forming an annular clutch component which is an advancement over conventional cold forming (Grob spline forming) processes.